Do the magic with automatic switching
C:\>cd %windir%\system32
C:\Windows\System32>mklink
Creates a symbolic link.
MKLINK [[/D] | [/H] | [/J]] Link Target
/D Creates a directory symbolic link. Default is a file
symbolic link.
/H Creates a hard link instead of a symbolic link.
/J Creates a Directory Junction.
Link specifies the new symbolic link name.
Target specifies the path (relative or absolute) that the new link
refers to.
C:\Windows\System32>mklink /D 11g D:\oracle\products\64bit\11203\bin
symbolic link created for 11g <<===>> D:\oracle\products\64bit\11203\bin
C:\Windows\System32>cd %windir%\SysWOW64
C:\Windows\SysWOW64>mklink /D 11g D:\oracle\products\32bit\11203\bin
symbolic link created for 11g <<===>> D:\oracle\products\32bit\11203\bin
and c:\windows\system32\11g to system wide PATH
@credit: http://www.howtogeek.com/howto/windows-vista/using-symlinks-in-windows-vista/
@credit http://realfiction.net/2009/11/26/Use-32-and-64bit-Oracle-Client-in-parallel-on-Windows-7-64-bit-for-eg-NET-Apps/